The present invention relates to an apparatus and method for providing information resources, such as those that are available over the Internet, via a broadcast channel. In particular, Uniform Resource Locators (URL) which identify the information resources are mapped to broadcast addresses which identify where the information resources are carried in a one-way broadcast television signal or the like. Although the system provides only one-way communication from the information provider, it has the look and feel of a bi-directional Internet connection.
Recently, an information network known as the "Internet" has become increasingly popular. The Internet provides a vast amount of information which may be accessed by users via computers for business, educational, and entertainment purposes. In particular, the Internet includes a large collection of interconnected documents which are stored in computers all over the world in a system known as the World Wide Web (i.e., the Web). The documents are organized into web spaces, where a web space includes a home page and links to other documents which may be in the local web space or in an external web space. Such links are known as hyperlinks. Documents may include moving images, text, graphical displays, and sound.
Internet resources are typically accessed in a two-way environment via a network connection. For example, connectivity to the network may be via a conventional twisted-pair telephone line which has a relatively low data-carrying capacity (e.g., bandwidth), or via a higher bandwidth path, which may comprise optical fiber and/or coaxial cable. To retrieve data from a network destination (e.g., an Internet site), a user sends a message to the network destination to request the transfer of information to the user's computer. The network destination typically includes a computer server known as a "nameserver."
FIG. 1 is a schematic diagram of a prior art process for enabling a user to request information through a nameserver. A user 10 sends a request signal to the nameserver 20. The nameserver 20 then sends a request signal to a source function 30, which may be a memory which is coupled to the server. The source function 30 includes the user-requested information which may comprise, for example, text, graphics, audio and/or video data. In response to the request signal from the nameserver 20, the source function 30 provides the requested information to the user 10. As discussed below, a user can communicate with the nameserver and the rest of the network via a number of protocols.
Source information which is stored in the source function 30 is often stored in a format known as "Hypertext Markup Language (HTML)". This file or script format allows the display of text, graphics and audio information, and provides links to other pages of information through "hyperlinks." Hyperlinks are strings of characters in a particular format that specify the address of the desired page of information.
In particular, HTML is a system for marking documents to indicate how the document should be displayed, and how various documents should be linked together. HTML is a form of Standard Generalized Markup Language (SGML), defined by the International Standards Organization (ISO), reference number ISO 8879:1986. HTML specifies the grammar and syntax of markup tags which are inserted into a data file to define how the data will be presented when read by a computer program known as a "browser". The data file, which is typically stored on a Web server, includes one or more Web pages which are visited by users who have computers which may run different browsers. When a page is visited, HTML data is downloaded to a user's computer. The computer's browser processes the data to format a layout for the page so the page can be viewed by the user on a computer screen. Generally, HTML tags provide text formatting, hypertext links to other pages, and links to sound and picture elements. HTML tags also define input fields for interactive Web pages.
Hypertext is so-named because it allows a user to access different pages in different orders using hyperlinks, rather than in a predetermined, linear manner. Moreover, a particular hypertext application known as "hypermedia" includes elements other than text, such as images, video, and audio. HTML can specify links to multimedia objects. Links in an HTML hypertext page usually appear as highlighted text which is known as the anchor of the link. Moreover, an image, such as an icon, can be an anchor which is activated, for example, by the user clicking on the icon using a mouse or other pointing device. Furthermore, images known as image maps can include a number of regions which are themselves individual anchors.
An HTML application is made available to users on the Web by storing the HTML file in a directory that is accessible to a server. Such a server is typically a Web server which conforms to a web browser-supported protocol known as Hypertext Transfer Protocol (HTTP). Servers that conform to other protocols such as the File Transfer Protocol (FTP) or GOPHER may also be used but do not support interactive HTML files.
HTTP defines a set of rules that servers and browsers follow when communicating with each other. Typically, the process begins when a user clicks on an icon in an HTML page which is the anchor of a hyperlink, or the user types in a Uniform Resource Locator (URL), described below. A connection is then made to the server at the address and port number specified by the URL. Next, the browser sends a request to retrieve an object from the server, or to post data to an object on the server. The server sends a response to the browser including a status code and the response data. The connection between the browser and server is then closed.
The URL is a unique address which identifies virtually all files and resources on the Internet. A URL has the form: EQU method://server:port/path/file#anchor.
The "method" of accessing the resource is the web browser-supported protocol, and may include, for example, HTTP, FTP, GOPHER, TELNET, NEWS, or MAILTO. The "server:port" indicates the name of the server which is providing the resource, and is alternatively known as the Internet domain name. For example, many companies will use their company name as part of the server field. The port designation is the port number on the server, but is usually not used since a default port is assumed. The "path" indicates the directory path to the resource. The file indicates the file name of the resource. The "anchor" indicates the named element in the HTML document. Not all fields are required.
For example, consider the following URL: EQU http://www.company.com/news/june.html.
The access method is HTTP, the server is www.company.com, there is no port specified, the path is news, the file is june.html, and there is no anchor. Examples of FTP, GOPHER, TELNET, NEWS, and MAILTO URLs are, respectively: EQU ftp://ftp.uu.net/doc/literary/obi/World.Factobook; EQU gopher://gopher.micro.umn.edu/; EQU telnet://compuserve.com/; EQU news:alt.cows.moo; and EQU mailto:president@whitehouse.gov.
Further information on URL formats may be found in an Internet document known as "Request for Comment (RFC) 1738" by T. Berners-Lee et al.
Thus, it can be seen that web browsers operate in a two-way communication environment to access information by sending a request signal defined by a URL command to a server, and receiving information in return. However, in a broadcast signal such as a television broadcast signal or the like, the communication is generally one-way, so there is no communication path to carry a user request signal. That is, in a broadcast environment, for example, including satellite, multiple microwave distribution systems (MMDS), terrestrial, and most cable transmissions, there is no mechanism to carry information from the user to the server (e.g., broadcaster).
Nevertheless, in view of the rapidly increasing use of Web pages and other Internet resources, it would be advantageous to provide a system for allowing users to access such resources via a broadcast data stream. The system should allow a user to select from a range of information which is carried in the broadcast stream by invoking a command which is defined according to a standard URL format. Furthermore, the system should be compatible to the extent possible with existing transmission and receiving equipment including set-top decoders and the like, and should further be compatible with current communication protocols such as those for the transmission of television signals. The present invention provides a system having the above and other advantages.